The school has 4000 books, and bought a book, now there are a total of______ Ben

The school has 4000 books, and bought a book, now there are a total of______ Ben

Now there are: 4000 + a (Ben). A: there are 4000 + a (Ben). So the answer is: 4000 + a

There are 15000 books in the school library, which is 3000 more than the original. How much more?

3000÷(15000-3000)=25%

There were 5200 books in the school library, and the number of books increased by 25% this year?

6500

To solve the equation: three fifths times one half plus x equals three fourths, four times one fourth x equals three fourths

The first question is 11 out of 20, and the second one is negative half

Who can tell me when to use the triangle and parallelogram rule of vector?

In fact, the two rules are essentially the same, there is no difference, just the starting point of the vector is different, the end point of a vector is the starting point of another vector, use the triangle, the same starting point of two vectors use the parallelogram rule, but you can also translate a vector and then use the triangle rule, in fact, after all

School autumn shared 10 buses, bus limit: 100 people, minibus: 60 people, the bus a total of 520 people more than the minibus, the size of the bus several

If there are x buses, there will be 10-x minibuses
100x-60×（10-x）=520
x=7
Then 10-7 passenger cars = 3

1，2，3，… Of the 98 natural numbers, the number that can be expressed as the square difference of two integers is___ ．

For x = n2-m2 = (n + m) (n-m) (1 ≤ m ＜ n ≤ 98, m, n is an integer), because n + m and N-M are odd and even, so x is odd or multiple of 4. Among 98 natural numbers from 1 to 98, there are 49 odd numbers and 24 divisible by 4, so there are 49 + 24 = 73 numbers satisfying the condition

It is proved that cN1 + 2cn2 + 3cn3 +. + ncnn = n 2N-1

You should know: KCNK = k * n! / [K! (n-k)!] = n (n-1)... (n-k + 1) / (k-1)! = n c (n-1) (k-1) KCNK = n c (n-1) (k-1) then: cN1 + 2cn2 + 3cn3 +. + n CNN = 1 * cN1 + 2cn2 + 3cn3 +. + n CNN = NC (n-1) 0 + NC (n-1) 1 +... + NC (n-1) (n-1) = n [C (n-1) 0 + C (n-1) 1 +... + C (n-1) (n -...]

If a bus carries 20 more people than a van, how many people can each van carry
A total of 720 teachers and students go out for tourism. A bus carries 20 more people than a van. Six buses and eight bread trucks carry the same number of people. How many people can each van take

Let's assume that the number of customers is x and the number of bread is y
According to the meaning of the title, the formula 6x = 8y, X-Y = 20
x=20+y
6(20+y)=8y
y=60 x=80
A: each van can take 60 people

lim x→∞ (1-x^2)/(2x^2-3) =lim x→∞ (1/x²-1)/(2-3/x^2) =-1/2
lim x→∞ (1-x^2)/(2x^2-3)
=lim x→∞ (1/x²-1)/(2-3/x^2)
=-1/2
Explain why we divide by x ^ 2,
There is a second step
=lim x→∞ (1/x²-1)/(2-3/x^2)
How do you figure it out to be - 1 / 2
I remember how to calculate, so that I can close the problem

-- landlord is awesome.